linux-kernel - Re: [PATCH v14 2/5] dma-buf: heaps: Add heap helpers

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Date:   Mon, 4 Nov 2019 11:36:12 -0800
From:   John Stultz <john.stultz@...aro.org>
To:     Sandeep Patil <sspatil@...gle.com>
Cc:     lkml <linux-kernel@...r.kernel.org>,
        Laura Abbott <labbott@...hat.com>,
        Benjamin Gaignard <benjamin.gaignard@...aro.org>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Liam Mark <lmark@...eaurora.org>,
        Pratik Patel <pratikp@...eaurora.org>,
        Brian Starkey <Brian.Starkey@....com>,
        Vincent Donnefort <Vincent.Donnefort@....com>,
        Sudipto Paul <Sudipto.Paul@....com>,
        Christoph Hellwig <hch@...radead.org>,
        Chenbo Feng <fengc@...gle.com>,
        Hridya Valsaraju <hridya@...gle.com>,
        Hillf Danton <hdanton@...a.com>,
        Dave Airlie <airlied@...il.com>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        sspatil+mutt@...gle.com, "Andrew F . Davis" <afd@...com>,
        Alistair Strachan <astrachan@...gle.com>
Subject: Re: [PATCH v14 2/5] dma-buf: heaps: Add heap helpers

On Mon, Nov 4, 2019 at 11:34 AM John Stultz <john.stultz@...aro.org> wrote:
>
> On Sun, Nov 3, 2019 at 8:13 AM <sspatil@...gle.com> wrote:
> > On Fri, Nov 01, 2019 at 09:42:35PM +0000, John Stultz wrote:
> > > Add generic helper dmabuf ops for dma heaps, so we can reduce
> > > the amount of duplicative code for the exported dmabufs.
> > >
> > > This code is an evolution of the Android ION implementation, so
> > > thanks to its original authors and maintainters:
> > >   Rebecca Schultz Zavin, Colin Cross, Laura Abbott, and others!
> > >
> > > Cc: Laura Abbott <labbott@...hat.com>
> > > Cc: Benjamin Gaignard <benjamin.gaignard@...aro.org>
> > > Cc: Sumit Semwal <sumit.semwal@...aro.org>
> > > Cc: Liam Mark <lmark@...eaurora.org>
> > > Cc: Pratik Patel <pratikp@...eaurora.org>
> > > Cc: Brian Starkey <Brian.Starkey@....com>
> > > Cc: Vincent Donnefort <Vincent.Donnefort@....com>
> > > Cc: Sudipto Paul <Sudipto.Paul@....com>
> > > Cc: Andrew F. Davis <afd@...com>
> > > Cc: Christoph Hellwig <hch@...radead.org>
> > > Cc: Chenbo Feng <fengc@...gle.com>
> > > Cc: Alistair Strachan <astrachan@...gle.com>
> > > Cc: Hridya Valsaraju <hridya@...gle.com>
> > > Cc: Sandeep Patil <sspatil@...gle.com>
> > > Cc: Hillf Danton <hdanton@...a.com>
> > > Cc: Dave Airlie <airlied@...il.com>
> > > Cc: dri-devel@...ts.freedesktop.org
> > > Reviewed-by: Benjamin Gaignard <benjamin.gaignard@...aro.org>
> > > Reviewed-by: Brian Starkey <brian.starkey@....com>
> > > Acked-by: Laura Abbott <labbott@...hat.com>
> > > Tested-by: Ayan Kumar Halder <ayan.halder@....com>
> > > Signed-off-by: John Stultz <john.stultz@...aro.org>
> >
> > I have one question and a naming suggestin below (sorry).
> >
> > Acked-by: Sandeep Patil <sspatil@...roid.com>
>
> > > +
> > > +static void dma_heap_buffer_vmap_put(struct heap_helper_buffer *buffer)
> > > +{
> > > +     if (!--buffer->vmap_cnt) {
> >
> > nit: just checking here cause I don't know the order in which vmap_get() and
> > vmap_put() is expected to be called from dmabuf, the manual refcounting
> > based map/unmap is ok?
> >
> > I know ion had this for a while and it worked fine over the years, but I
> > don't know if anybody saw any issues with it.

Sorry, I hit send before replying to this bit. I'll double check on this.

thanks again for the review!
-john